The availability of rechargeable batteries has led to a variety of rechargeable battery-operated "cordless" devices including grass shears, hedge trimmers, toothbrushes, shrub trimmers, lawn mowers, flashlights, sprayers, screwdrivers, and the like. In some cases the batteries are housed in a nonremovable pack. The recharging circuitry usually comprises a separare charging unit. In some cases the charging circuitry is incorporated as a part of a rechargeable battery pack. It has also been previously proposed to provide a removable battery pack having its own recharging circuitry, the pack having AC type prongs and arranged so that the pack can be interconnected through the prongs to the device to be powered or through the same prongs to a household receptacle for recharging. It has also been suggested to have a removable rechargeable battery pack that could be connected to any one of several battery power consuming devices. This concept has been proposed both for portable pocket size cordless apparatus as well as heavier portable cordless apparatus such as a cordless hedge trimmer but only for a fixed energy requirement.
A representative collection of prior art patents dealing with the foregoing constructions includes U.S. Pat. Nos. 1,506,302; Ser. No. 427,480, Zdansky (A.P.C.), published June 15, 1943; 2,628,339; 2,818,498; 2,876,410; 2,982,881; 2,995,695; 3,013,198; 3,021,468; 3,027,507; 3,067,373; Re. 25,388; 3,109,132; 3,120,632; 3,145,404; 3,183,538; 3,275,819; 3,280,351; 3,281,636; 3,329,881; 3,360,708; 3,447,058; 3,533,119; 3,623,223; 3,742,832; 3,757,194 and 3,883,789.
In a more recent development, a system now on the market is directed to a range of cordless devices including grass shears, lanterns, drills, and shrub trimmers. Each device mates with a standardized "power handle" which serves both as a handle and to contain a rechargeable battery. This handle is required to be removed and placed in a stand-type charger for recharging. Such a system points up the advantages of standardizing the power unit portion of a cordless device. However, this system makes no provision for the power handle to be used except singly. There is no provision for varying the amount of available battery power even though one device in the system might require more or less battery power than another. Also, the power handle in such a system does not, itself, contain recharging circuitry and the handle is not adapted to be plugged directly into a household receptacle for recharging.
Despite the extensive development of the art, there has not heretofore been provided a family of cordless portable tools or devices characterized in respect to each device in the family having one or a plurality of outwardly opening pockets adapted to receive a corresponding number of identical rechargeable battery packs according to the energy and power requirements of the individual devices and which packs can be recharged from a household receptacle through the same prongs used for discharge. Further, the prior art has not provided a relatively flat, rectangular-shaped battery pack that can be installed and removed from the particular device with the prongs arranged so as not to require guideways for sliding the pack and so as to minimize the hazard of dropping the pack.
With all of the foregoing considerations in mind, it thus becomes the object of this invention to provide a type of construction for mass production of a wide range family of portable cordless devices which for each device can be duplicated with respect to incorporating a standardized selected number of battery pack receiving pockets in the device and providing a standard type of rechargeable battery pack unit incorporating recharging circuitry and which can be used singly or in plural groups corresponding to the number of pockets in the particular device and which can be safely placed in an ordinary household receptacle for recharging purposes.